For some reason (probably I'm an idiot) I can't plug in the numbers. I'm using the google account. Does someone know where I'm going wrong? Also this site is fantastic. I've already told everyone I know that smokes about it. Thanks, SPM

I had to update the link to the calculator site on my original post. If you have saved the location as a favorite in the past the link will no longer work. Sorry for any problems this may have caused. The new link appears to work fine.

Also you will notice that the link to the MS Works spreadsheet is no longer listed on the web page. It was not working correctly so I removed it.

Thanks Tom, I thought the air intake to firebox and opening from the firebox to the main chamber looked rather large. That expains it. I'm glad I put my design out there for a sanity check. These changes are easy to make at this point. That's a great calculator. Thanks for sharing that with us.

Hey Tom, I have a few questions for you and whoever is familure with the calculator. Is it ok for my firebox to be half the size instead of a third? Also the calculator says I need a firebox to chamber opening of 57, when I scroll down it give me an opening of 157. Do I make it bigger or try to achieve 57. My dimensions are: fire box is 18"x22" dia, chamber is 36"x22" dia, and I have a 4" stack. Thanks, SPM

For the firebox to cooking chamber opening I entered 7.8" by 7" to get the volume as close to the 54.71 listed above. The calculator showed that 7.8" x 7" = 54.6 sq. in. the calculator indicated that I would only need 1 opening of that size indicated in the blue cell to the right.

You can change the dimensions of the opening to anything that will fit for you but you need for the blue cell on the right to indicate the need for 1 or slightly less than one for the opening to be big enough.

Example:

Instead of 7.8" by 7" you could enter 7" by 9.25" and the calculator indicates that you need .99 or one of these openings.
This allows you to change the opening size around to best fit your needs but still make sure you have the correct opening volume needed for airflow.